High Resolution Chronostratigraphic Constraints on Terminal Paleozoic Crises and Recovery in the Circum-Tethys Region

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ABSTRACTHigh Resolution Chronostratigraphic Constraints on Terminal Paleozoic Crises and Recovery in the Circum-Tethys RegionRoland Mundil, Kenneth R. Ludwig, Paul R. RenneThis research program is intended to improve the calibration of late Permian through Triassic biostratigraphic and magnetostratigraphic time scales towards an enhanced understanding of the terminal Paleozoic environmental and biotic crisis and subsequent Mesozoic recovery. Improved time scales are critical to realistic evaluation of the causes of, and interrelationships between, the various observed biotic and paleoenvironmental anomalies that characterize this transition. Our initial radio-isotopic age data (both U/Pb and Ar/Ar) are at variance with recent studies, many of which favor a rapid extinction caused by a bolide impact. Although an impact at or near the P-T boundary cannot be excluded a priori, a more gradual scenario and a causal relation between the massive continental basalt volcanism in South China at the end of the Permian and Siberia at the Permian-Triassic boundary - possibly in combination with other factors - and the biotic crisis must be considered. Despite the dramatic increase in available geochronologic data for the Late Permian through Early Triassic interval, crucial questions remain unanswered and will be addressed: 1) How synchronous are global biostratigraphic correlations across the Permo-Triassic boundary, and how precisely can biostratigraphic, geochemical, lithostratigraphic, and other records be correlated? 2) What are the temporal relations between terrestrial and marine records across the Permo-Triassic boundary? 3) What was the rate of the biotic recovery in the Early Triassic? 4) Do interlaboratory discrepancies (either physical or by interpretation) between high-precision U/Pb zircon ages for the Permo-Triassic boundary undermine the inferred extremely rapid chronology of extinction events? Indeed, how reliable is U/Pb zircon geochronology as a Phanerozoic time scale method?